Case Study

Summary

The New York City water supply provides more than one billion gallons of water each day to over nine million New Yorkers – nearly half the state’s population – and has been doing so for over 150 years. The water supply consists of 19 reservoirs and three controlled lakes with a total storage capacity of approximately 580 billion gallons. The water system is an engineering marvel, designed and built with various interconnections to increase operational flexibility by permitting the transfer of water from one system to another for improved water quality. Approximately 7,000 miles of water mains, tunnels, and aqueducts bring water to homes and businesses throughout the city and some upstate communities. In comparison to other public water systems, approximately 95% of the total water supply is delivered to the consumer by gravity. As a result, operating costs are relatively insensitive to fluctuations in the cost of power.

In the early 1990s the City embarked on an aggressive program to protect and enhance the quality of New York City’s drinking water. Based on an extensive water quality monitoring and research program, the City determined the key sources of pollutants were inadequately treated wastewater; wildlife, especially waterfowl; agriculture; and stormwater runoff from development. The City designed a comprehensive watershed protection strategy to target these primary sources of pollution, incorporating both protective and remedial initiatives. The watershed program provides an alternative to expensive end-of-pipe filtration treatment.